1. Field of the Invention
This invention generally relates to a linear motion guide unit and in particular to improvements in an end block of a linear motion guide unit.
2. Description of the Prior Art
A linear motion guide unit is well known in the art and it generally includes a rail extending over a length, a slider slidably mounted on the rail and a plurality of rolling members interposed between the rail and the slider. One prior art example of such a linear motion guide unit using rollers as the rolling members is illustrated in FIG. 10 and another prior art example using balls as the rolling members is illustrated in FIG. 11 . That is, as shown in FIG. 10 , a linear motion guide unit includes a rail 5 extending over a desired length and provided with a pair of inner guide grooves, formed on its opposite side surfaces, a slider 1 slidably mounted on the rail 5 and formed with a pair of outer guide grooves each located opposite to and spaced apart from a corresponding one of the pair of inner guide grooves of the rail to thereby define a pair of guide channels and a plurality of rollers 7. The linear motion guide unit shown in FIG. 10 is of the so-called indefinite type so that a pair of endless circulating paths is provided in the slider 1, each, of which is filled with a plurality of rollers 7. In the structure shown in FIG. 10, the rollers 7 are arranged in the so-called crossed roller arrangement so that any two adjacent rollers 7 are oriented such that their rotating axes extend perpendicular to each other when viewed in the direction of advancement.
Since the slider 1 is provided with a pair of endless circulating paths, the rollers 7 may roll along each of these circulating paths indefinitely as long as the rail 5 extends. As well known in the art, each of the endless circulating paths includes a load path section, which corresponds to a guide channel defined between a pair of associated inner and outer guide grooves, a return path section and a pair of curved connecting path sections connecting the corresponding ends of the load and return path sections.
The slider 1 typically has a three-part structure,
6 and a pair of front and end blocks 4 located at the front and rear ends of the center block, respectively. In the structure shown in FIG. 10, an end cover plate 19 is fixedly attached to each of the front and rear end blocks 4' and a grease nipple 15 is provided in the rear end block 4 for allowing to supply grease into a desired location inside the slider 1. The linear motion guide unit illustrated in FIG. 11 is similar in many respects to the linear motion guide unit illustrated in FIG. 10 excepting the fact that use is made of balls 8 in place of rollers 7.
Since the slider 1 has basically a three-part structure as described above, the center and end blocks 6 and 4 are separately fabricated and then they are assembled together as the slider 1. The front and end blocks 4 are fabricated substantially identical in structure. As best shown in FIG. 12, the end block 4' either front or rear, is formed with a curved connecting path section 2 of an endless circulating path. Thus, the rollers 7 may move from the load path section to the return path section or vice versa through each of the pair of curved connecting path sections 2.
Such an end block is typically fabricated from a resin material, for example, by injection molding. In such a case, however, in order to attain a desired accuracy in manufacture, it is desired that the end block 4 be uniform in thickness as much as possible. However, since the end block 4 must be formed with a curved connecting path section of an endless circulating path as described above, the end block 4 is typically constructed to have a grid-shaped rib structure 13 as best shown in FIG. 1. Because of the provision of such a grid-shaped rib structure 13, a number of recesses 3 are defined.
However, the provision of such a number of recesses 3 tend to degrade the structural integrity of the end block 4 and in the worst case the end block 4 may distort or suffer damage under severe use conditions, such as application of a relatively large load. In addition, these recesses 3 have been found to be a source of relatively large noise which is created when the slider 4 slides along the rail 5. In particular, when the rollers 7 or balls 8 roll along the curved connecting path section of an endless circulating path, the rattling noise appears to be amplified due to the presence of such a large number of recesses 3.